This document relates to electromagnetic spectrum allocation and utilization.
Given any particular signal power relative to noise, it is possible to achieve the highest channel capacity by spreading a signal across as much spectrum as possible. Thus, optimal utilization of spectrum may be achieved by spreading a signal across as much spectrum as possible, e.g., optimal channel capacity can be achieved by making a signal as much like Additive White Gaussian Noise as possible.
This aspect of spectrum utilization also provides for uncoordinated band allocation in which a signal in the band appears as noise in relation to other signals in the band. Such uncoordinated band allocation results in optimal cumulative spectrum utilization. Utilization can be increased using Multiple-Input, Multiple-Output (MIMO), which uses multiple antennas at both the transmitter and receiver to improve communication performance. MIMO increases spectrum capacity in accordance with the number of transmit antennas and receive antennas above what could otherwise have been achieved because the number of independent channels available in a given spectrum band is increased.
The use of multiple transmit and receive antennas in the MIMO array, however, increases the complexity of recovering the communications on any given channel. MIMO processing involves matrix operations that are used to characterize the communications that are occurring over the channels of the MIMO array. As the number of antennas in the MIMO array increases, the size of the matrix operations used to characterize the communications likewise increase. In turn, the complexity of any computations also increases geometrically.